The present invention relates generally to fluid metering devices and, more particularly, to an apparatus for dispensing a precise volume of liquid by fluidic means.
Devices have been known for dispensing a precise or metered volume of liquid in a pulsated or periodic manner. Various apparatus, such as positive displacement pumps, have been employed to dispense metered volumes of liquid for various purposes. Such apparatus are capable of selective operation or operation by pulsations or cyclical controls. One of the problems with prior apparatus of the character described is in maintaining the precision of the devices due to wear or manufacturing tolerances in the various moving components of the apparatus. For instance, pistons and cylinders and their operative components become worn and adversely affect maintenance of precise volume dispensing. Seals are required for such devices and those components become worn as well. Manufacturing tolerances for all of the components of such apparatus is a constant problem requiring cost extensive quality controls.
Another problem with prior apparatus for dispensing metered volumes of liquid is that they often are affected by changes in pressure, viscosity or temperature influences on or in the liquid being dispensed. The prior apparatus may be preset to dispense accurate metered volumes of liquid, but pressure, viscosity or temperature changes can upset the preset or calibrated conditions of the apparatus.
The present invention is designed to overcome these problems by providing an apparatus for dispensing a precise volume of liquid by accurate metered controls which are totally independent of such changes in pressure, viscosity or temperature. This is accomplished by employing total fluidic controls which have no moving parts and which employ a fluid amplifier within the controls.